Determining the activation energy of a reaction, By using the experimental data and the Arrhenius equation, the activation energy for the reduction of peroxodisulphate ions, S2O82-(aq) by iodide ions, I-(aq) in a clock reaction is found to be approximatel

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Candidate Name: Teng, Eva Yi-Chun

Candidate Number: 001407-038

Determining the activation energy of a reaction

Data Collection

Data processing

Note: the rate constant, K is calculated as follows:

Graph

Note on graph: In this graph T is temperature in Kelvin and t is the time taken for the reaction to reach the blue-black colour stage. A R2 value is calculated in the graph above using Microsoft Excel. The R2 value – or the coefficient of determination, can be an indication of how closely the points relate to a line of best fit. It ranges from 0 to 1 with the latter indicating that the line of best fit can fully predict future points. The R2 value in this graph is found to be 0.9628, which is quite close to 1. This suggests that this linear line is a good fit of the points.

Calculating the activation energy

The Arrhenius equation states that,

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ln k =

where

k = rate constant

A = Arrhenius constant

E = activation energy

R = Universal gas constant = 8.31 J k-1 mol-1

T = temperature in Kelvin

This logarithmic form of the Arrhenius equation resembles a linear function in the form y = mx + b. The corresponding parts can be summarized as follow:

y   m   x   b

Since  = m, the activation energy can be determined by multiplying the gradient of the linear line of best fit on the graph above by the universal gas constant and -1. This is shown as ...

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